British patent specification No. 570,858 discloses various processes for making fiber forming polymers. It is clear that neither the novel dianhydrides nor the polyimides prepared therefrom, which are useful as moldings, fibers, laminates and coatings, have been contemplated in the prior art.
The general objective of this invention is to provide novel dianhydrides. A more specific object is to provide novel polyimides-polyamides and copolyimides-copolyamides based on I, II and diamines. Another object is to provide polyimides-polyamides based on either I or II and other dianhydrides with dicarboxylic acids and diamines or mixtures of diamines.
We have found that novel polyimides-polyamides can be formed by reacting dianhydrides of the following structure: ##STR1## wherein Z is either hydrogen or a benzene radical and dicarboxylic acids or their derivatives with diamines. The dicarboxylic acids having the following general formula: ##STR2## where X is OH, Cl, or O alkyl and R" is a divalent aromatic or aliphatic radical and wherein the O-alkyl group comprises about 1 to about 5 carbon atoms. Advantageously R is a divalent aliphatic hydrocarbon containing about 2-18 carbon atoms or aromatic divalent radical containing about 1-3 benzene rings, or heterocyclic hydrocarbon, or a mixture of these. Useful dicarboxylic acids include such acids or their halides or esters as oxalic, glutaric, adipic, azelaic, terephthalic, isophthalic, biphenyl-4,4'-dicarboxylic, 2,6-naphthalene dicarboxylic, and pyridine-2,4- and 3,5-dicarboxylic.
The dianhydrides are prepared by photocycloaddition reactions between 1-cyclohexene-1,2-dicarboxylic anhydride and 3,6-diphenyl-4-cyclohexene 1,2-dicarboxylic anhydride and photocycloaddition reactions between cis-4-cyclohexene-1,2-dicarboxylic anhydride and cis-1-cyclohexene-1,2-dicarboxylic anhydride. Both I and II react readily with a diamine to form a high-molecular-weight polyimide or copolyimide. In the novel process aliphatic, cycloaliphatic, araliphatic and aromatic diamines can be polymerized with I and II in the melt to form high molecular weight polyimides and copolyimides.
Dianhydrides that can be mixed with I or II in a ratio that ranges from about 10:1 to about 1:10 as monomers for the synthesis of copolyimides are characterized by the following formula: ##STR3## wherein R' is a tetravalent organic radical selected from the group consisting of aromatic, aliphatic, cycloaliphatic, heterocyclic, combination of aromatic and aliphatic, and substituted groups thereof. However, the preferred dianhydrides are those in which the R' groups have at least 6 carbon atoms, wherein the 4 carbonyl groups of the dianhydride are each attached to separate carbon atoms and wherein each pair of carbonyl groups is directly attached to adjacent carbon atoms in the R' group to provide a 5-membered ring as follows: ##STR4## The preferred dianhydrides mixed with either I or II, as recited above, yield upon reaction with the diamines copolyimide structures having outstanding physical properties. Illustrations of dianhydrides in addition to either I or II suitable for use in the present invention include: pyromellitic dianhydride; 2,3,6,7-naphthalene tetracarboxylic dianhydride; 3,3',4,4'-diphenyl tetracarboxylic dianhydride; 1,2,5,6-naphthalene tetracarboxylic dianhydride; 1,2,3,4-cyclopentane tetracarboxylic dianhydride; 2,2',3,3'-diphenyl tetracarboxylic dianhydride; 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride; 2,3,4,5-pyrrolidine tetracarboxylic dianhydride; 3,4,9,10-perylene tetracarboxylic dianhydride; bis(3,4-dicarboxyphenyl)ether dianhydride; ethylene tetracarboxylic dianhydride; 3,3',4,4'-benzophenone tetracarboxylic dianhydride; bis(3,4-dicarboxyphenyl)sulfide dianhydride; bis(3,4-dicarboxyphenyl)sulfone dianhydride; bis(3,4-dicarboxyphenyl)methane dianhydride; 1,4,5,8-naphthalenetetracarboxylic dianhydride; tricyclo[4,2,2,0.sup.2,5 ]dec-7-ene-3,4,9,10-tetracarboxylic dianhydride; 3,6-ethenohexahydropyrometallitic dianhydride; cyclobutane-1,2,3,4-tetracarboxylic dianhydride; and 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride; 1,2,3,4-tetramethyl-1,2,3,4-tetracarboxylic dianhydride.
Our process for the manufacture of the novel polyimides-polyamides comprises reacting about equal molar amounts of the dianhydride and dicarboxylic acid with a primary diamine or a mixture of primary diamines. The molecular ratio of the dianhydride to the primary diamine may be in the range of about 1.2 to 1 preferably in the range of about 1 to 1. The ratio of the dianhydrides to the dicarboxylic acid can be about 10:2 to about 2:10 preferably, about 1:2 to about 2:1. Suitably, the reaction is conducted as a batch reaction at a temperature of about 130.degree. C. to 300.degree. C. for a period of about 2 to 8 hours in a nitrogen-containing organic polar solvent such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide or pyridine. The polycondensation can also be carried out as a continuous process. The polycondensation can suitably be carried out at a temperature of 130.degree. C. to 300.degree. C., preferably at a temperature of 180.degree. C. to 250.degree. C. The novel polyimides-polyamides of this invention have the following recurring structure wherein R is a divalent aliphatic or aromatic hydrocarbon radical and Z is a hydrogen or benzene radical: ##STR5## The radical R" may be divalent aliphatic hydrocarbons of 2 to 18 carbon atoms or an aromatic hydrocarbon from 6 to 20 carbon atoms, or an aromatic hydrocarbon radical containing from 6 to 10 carbon atoms joined directly or by stable linkage comprising --O--, methylene ##STR6## --SO--, --SO.sub.2 --, and --S-- radicals. R is an aliphatic radical comprising about 2 to 18 carbon atoms or an aromatic hydrocarbon comprising 6 to 20 carbon atoms and is derived from the dicarboxylic acids discussed herein.
The radical R" is derived from aliphatic, araliphatic or cycloaliphatic diamines such as ethylenediamine, propylenediamine, 2,2-dimethylpropylene diamine, tetramethylene diamine, hexamethylene diamine, octamethylene diamine, nonamethylene diamine, decamethylene diamine, dodecamethylene diamine, 4,4'-diaminodicyclohexylethane, xylylene diamine and bis(aminomethyl)cyclohexane. Suitable aromatic diamines useful in Applicant's process include para- and meta-phenylenediamine, 4,4'-oxydianiline, thiobis(aniline), sulfonylbis(aniline), diaminobenzophenone, methylenebis(aniline), benzidine, 1,5-diaminonaphthalene, oxybis(2-methylaniline), thiobis(2-methylaniline), and the like. Examples of other useful aromatic primary diamines are set out in U.S. Pat. No. 3,494,890 (1970) and U.S. Pat. No. 4,016,140 (1972) both incorporated herein by reference. The preferred diamines are hexamethylene diamine, dodecamethylene diamine and 4,4'-oxydianiline.
In some cases the polyimide-polyamide may be further polymerized under "solid state polymerization" conditions. The term solid state polymerization refers to chain extensions of polymer particles under conditions where the polymer particles retain their solid form and do not become a fluid mass. The solid state polymerization can be carried out below the melting point of the polyimide and can be conducted in several ways. However, all techniques require heating the ground or pelletized polyimide below the melting point of the polyimide, generally at a temperature of about 175.degree. to 300.degree. C. while either sparging with an inert gas, such as nitrogen or operating under vacuum. In cases where the polyimides have a low melt temperature, they can be polymerized in the melt under vacuum in thin sections or using thin film reactors known in the art.
Injection molding of the novel polyimide-polyamide is accompanied by injecting the polyimide into a mold maintained at a temperature of about 25.degree. C. to 150.degree. C. In this process a 20 second to 1 minute cycle is used with a barrel temperature of about 125.degree. C. to 350.degree. C. The latter will vary depending on the Tg of the polymer being molded.
The novel polyimides-polyamides have excellent mechanical and thermal properties and can readily be molded into useful articles or formed into fibers, films, laminates or coatings. Infrared spectra of the polyimides-polyamides have confirmed the polyimide-polyamide structure. Glass transition temperature Tg of the polyimide-polyamide varied with the particular diamine used as shown in the Examples. Values range from a Tg of 70.degree. C. to 180.degree. C.
Diamines with the amino groups attached directly to the aromatic ring are suitably polymerized with I or II by solution condensation in organic polar solvents. We have found that the polyimides-polyamides and copolyimides-copolyamides of this invention are improved by the addition of reinforcing material. Suitably about 25 to 60 percent by weight glass fibers, glass beads or graphite or mixtures of these can be incorporated into the polyimides and copolyimides. Any standard commercial grade fibers, especially glass fibers may be used. Glass beads ranging from 5 mm to 50 mm in diameter may also be used as reinforcing material. Injection molding of the novel glass-filled polyimide-polyamide is accomplished by injecting the polyimide into a mold maintained at a temperature of about 50.degree. C. to 150.degree. C. In this process a 25 to 28 second cycle is used with a barrel temperature of about 125.degree. to 350.degree. C. The injection molding conditions are given in Table 1.
TABLE 1 ______________________________________ Mold Temperature 50.degree. to 150.degree. C. Injection Pressure 15,000 to 19,000 psi and held for 1 to 3 seconds Back Pressure 100 to 220 psi Cycle Time 25 to 28 seconds Extruder: Nozzle Temperature 125.degree. C. to 350.degree. C. Barrels: Front Heated to 125.degree. C. to 350.degree. C. Screw: 20 to 25 revo- lutions/minute ______________________________________